Help with editing a song?

I want to edit Coronation and Babu Yetu from Civilization IV by Christopher Tin. I want the instrumental version as in no singing. I want to edit the song to be a little slower and in waltz time (in three for the beggining and three or four for the second half). Any help on how to edit the song, what to use or if you could just give a link or something that you edited. Thanks.